The U.S. Supreme Court is allowing Idaho property owners to challenge the wetlands designation for their property in a case that had generated landowner sympathy among conservatives, libertarians and developers.

The property owners, Chantell and Michael Sackett, were represented by the Pacific Legal Foundation, which had viewed the case as one of the top five before the court in 2012.

Justice Antonin Scalia wrote the opinion (PDF) for the unanimous court in favor of the Sacketts. A concurrence by Justice Samuel A. Alito Jr. goes further with a nod to property rights implications and a call for congressional action.

“The position taken in this case by the federal government—a position that the court now squarely rejects—would have put the property rights of ordinary Americans entirely at the mercy of Environmental Protection Agency (EPA) employees,” Alito wrote.

The Sacketts sought to file a federal suit challenging an “administrative compliance order” issued in 2007 by the Environmental Protection Agency after they begin filling in their lot north of Priest Lake. They claimed the order was arbitrary and capricious under the Administrative Procedure Act and it deprived them of property without due process under the Fifth Amendment. In their view, their property is not a wetlands subject to the Clean Water Act.

Scalia said the Clean Water Act does not bar the Sacketts’ federal civil suit, filed after the EPA refused to hold a hearing but before any fines were issued. If the Sacketts had waited for the EPA to initiate a civil action, Scalia said, “each day they wait for the agency to drop the hammer, they accrue, by the government’s telling, an additional $75,000 in potential liability.” He concluded that the compliance order was a final agency action, and there was no other adequate remedy than APA review.

Justice Ruth Bader Ginsburg wrote a separate concurrence saying she understands the opinion applies only to suits contesting EPA authority to regulate land, rather than the terms and conditions of compliance orders.

Alito’s concurrence criticizes the Clean Water Act and says Congress needs to act. “The reach of the Clean Water Act is notoriously unclear,” he wrote. “Any piece of land that is wet at least part of the year is in danger of being classified by EPA employees as wetlands covered by the Act, and according to the federal government, if property owners begin to construct a home on a lot that the agency thinks possesses the requisite wetness, the property owners are at the agency’s mercy.”

Alito went on to write of the potential for daily fines that could reach millions of dollars for homeowners who wait for the EPA to sue. “In a nation that values due process, not to mention private property, such treatment is unthinkable,” he writes. “The court’s decision provides a modest measure of relief. At least, property owners like petitioners will have the right to challenge the EPA’s jurisdictional determination under the Administrative Procedure Act. But the combination of the uncertain reach of the Clean Water Act and the draconian penalties imposed for the sort of violations alleged in this case still leaves most property owners with little practical alternative but to dance to the EPA’s tune.”

Alito goes on to call on Congress to clarify EPA jurisdiction in Clean Water Act cases with “a reasonably clear rule.”